Hey everyone,
I've got a '92 Civic VX as my commuter car, have to renew registration and it's smog year so took it down to the shop to get it tested and it failed massively. The Hydrocarbons are in the gross polluter range at 2500 rpm. My EGR failed the functionality test as well so that's where I started.

As soon as I took it off I knew something was wrong because some previous owner had put a strip of aluminum tape over the ports in the manifold blocking off the EGR. Took that off and moved on. The EGR works, I applied vacuum straight from the manifold and the engine stalled pretty much immediately.
I get vacuum signal all the way up to the inlet of the EGR Frequency Solenoid up on the fire wall, but no vacuum past it. I have 12v at the plug which I'm not sure is right, I thought it was only supposed to have 12v over 2000rpm? I tried it with it plugged in and not plugged in and still no vacuum signal. I took the solenoid out and tried it on the workbench and the solenoid does click but the ports must be clogged or something.
Since they're not made anymore has anyone repaired one of these? Is there a substitute available?

 

Most solenoids have one wire connected to a constant source of +12 volts and the ECU pulls the other wire to ground to activate the solenoid. When the solenoid is not active you will measure +12 on both wires.

You may have the wrong ECU. Also the hoses could be hooked up wrong. It's clear that someone else has been in there before and who knows what they did. A VX requires a complete set of VX parts to work properly. You can't mix and match from the non-VTEC-E models. Identify what you have.

The main effect of the EGR is to reduce NOx. Gross amounts of HC are likely some other problem entirely.

 

Okay I'll check on that, does the service manual show correct part numbers in it? I've got a PDF copy of that I can go through.

Vacuum hoses are hooked up correctly according to the manual, but I will do some more testing of the solenoid. I'll try and hook up my little hand vacuum pump to one side and a vacuum gauge to the other and apply power to the solenoid.

Since all this was caused by needing to get smogged, what would the HCs come from? Where should I look to repair that?

All the ignition is pretty new, just replaced at the end of last year new wires, plugs, rotor, cap, ignitor, and coil.
Valve adjustment was just set with the last oil change.

 

you'll need to verify if the egr is working and go from there. You might need to clean out the egr passageways as they can get gunked up. We had a member 5yrs ago take his HX to a mechanic to clean out the passageways because the regular stuff he used from parts stores weren't working.

 

You might try replacing the oxygen sensor, it is important to the D15Z1 running properly especially under light load. Expensive though.

 

The EGR Valve works, when I applied vacuum to it at idle the engine stalled. I cannot get vacuum signal from the solenoid so I believe that to be faulty but want to test it more thoroughly first.

Due up this weekend is a new PCV valve, cleaning the IM (new gasket ordered and egr valve gasket ordered.) and setting/confirming spark timing.

Hopefully I can get the solenoid working and it'll be all good, has anyone repaired one of these solenoids before?

 

Alright so ran through the factory manual EGR system test and it seems like it's all working good. Got 8" of vacuum to the EGR valve hose, and applying 8" of vacuum to the EGR valve made the engine bog down. There is a little bit of gunk under it in the IM but certainly not blocked.
Timing was a bit advanced so reset it to stock.
PCV valve is new and operational.
Cleaned the filter housing and hose to the TB, and replaced the air filter.
Spark plugs are the correct type with correct gap, they were a nice light tan but the edges by the threads had some black carbon looking deposits.

The smog place re-tested and I'm doing a lot better but still not enough to pass yet.
Any other thoughts?
When I have time I'll clean the IM still, but didn't get a chance to do it today. It's got welded plugs so I'll have to drill it out.

 

Another update. EGR system is all functional as stated above. Cleaned the IM as best I could, it wasn't super bad to start with but got all the deposits off and cleaned out the second straight PCV under the IM and the hose to it as well as all attached sensors and the TB etc. Got it all back together and then had to replace the thermostat as it got stuck open at some point (unrelated to IM but still worth mentioning I figure) bled coolant afterwards.

Took it to smog again and it was even worse than the first time?!

Now I smell gas occasionally at idle so I need to check for leaks from pulling the IM. I also still sometimes get an unsteady idle even though I've bled coolant a few times and cleaned out the IACV again when the IM was off.

I put a new O2 sensor in (proper NGK 24300 model) and have not noticed a change in driving yet but hasn't been smogged since I put it in.

This is getting frustrating so any help would be appreciated!

 

So you ignored the high HC and thought fixing the egr valve would magically solve that? Did you do any research into what causes high HC levels before you wasted money failing smog again?

 

HC's and EGR not directly related but the EGR system got failed the first time in the functional test so it needed fixing anyways.

HC's are from too rich or too lean a mixture if I've been reading right. Or possibly oil/coolant leaks. Also possible is weak spark, but distributor components are all new as of last summer and shouldn't be failing that soon. Other suggestions included cleaning the IM, making sure both PCV's and their hoses were clear and working.

I've read through all the threads I could find related to the VX and smog and did everything I could from those.

 

HC emissions is unburned fuel. You need to post the entire results if you're seeking help as you cannot diagnose an emissions problem without looking at the entire gas analysis. It could be anything from a leaking injector to loose valve clearances.

 

Alright the first test is as follows.


The next two times the just ran the pre-test, but they did give me a printout of the latest one (The worst one, second time was the best but didn't get a printout).

 

1) Compression test the cylinders.
If compression is good and nearly identical in all 4 cylinders...

2) Install new plugs, wires, cap and rotor and set the ignition timing.

Then have engine emission tested again.

 

Less than 10% difference on the compression test: 185, 183, 182, 193. All plugs out and TB open, and tried keeping the cranking time as close as possible as well.

I'll try that and report back.

 

Just got back from smog, they've been nice enough to just run the pre-test real quick and let me know numbers without charging me an arm and a leg every time.

Drove around for a bit before stopping at smog, and with new OEM cap and rotor and new good quality wires and new plugs last week still horrible numbers. About 400 at idle and 300 at 2500.

 

Alrighty, I'm back for more. Rebuilt the engine, oil rings were bad and was burning some oil causing the high HCs. Got it re-tested and everything is looking awesome EXCEPT my CO at 2500 rpm is too high. The cause of this would be running rich right? What would be the cause of it running rich though? What can I test to find out?

 

O2 sensor dying?

 

Make sure the engine is reaching full operating temperature and going to closed loop mode. Test the ECT with an ohmmeter when hot.

Is the exhaust manifold cracked? Air leak before the O2 sensor will cause it to read wrong and richen the mixture.

If all three pollutants (HC, CO, and NOx) are close to or over the limit, the catalytic converter may be worn out.

 

O2 sensor is almost brand new so unlikely to be the issue. It is the correct one for the VX model as well.

Other pollutants are really good now that the motor is rebuilt. I’ve attached a photo of the printout.

Also I think EGT and exhaust manifold are okay. Will double check though. I’ll also make sure exhaust nuts are all tight.

 

Just because the 02 is new doesn't mean it's working correctly! I have an HX, similar to your VX and had the same problem when I had a faulty 02 sensor, got a new one, that was defective! I tested it with an multimeter set to ohms. The resistance was infinity! Yup, was bad! Got another one and bam! worked well.. So don't assume just because it's new, that it's working.

 

I won't rule out the O2 sensor, but I'll have to read up on how to check it.

ECT read 330 ohms maybe 5 minutes after shut down after a drive. From what I can tell that lines up okay with the chart in the factory service manual.

Forgot to mention but when cruising above about 60mph it is hard to hold steady. It feels like it surges in and out of power randomly. I'm pretty certain I have the CA model so without lean burn, so maybe that is part of the problem? It's not a drastic issue but it doesn't hurt to mention it.

Also check engine light is only on for a few seconds after the key is moved to ignition then it goes out, if car is started it does not stay lit. Doesn't flash any codes when service connector is jumped. So that doesn't give me any leads.

 

Its not going to flash a code until you put it in service mode.

You'll need to verify that the ecu is from cali and not a fed. If its a fed ecu its probably going into lean burn.

 

service connector wasn’t (edit* was, autocorrect got me) jumped and ignition on so should have been in service mode?

and 90% sure it’s Cali from when I checked it back before rebuilding the motor.

 

How is it going to be in service mode without the service connector jumped? Pretty sure isn't good enough. Post a pic of the ecu label.

 

Whoops my bad, posting some of these from my phone and autocorrect got me on that one. It was jumped and didn’t flash any codes when in service mode.

Here’s the best picture of the ECU I can get at the moment.